Such a vertical Hall sensor is a magnetic field sensor which is sensitive to a magnetic field which extends parallel to the surface of the semiconductor chip. The Hall sensor usually consists of an n-doped well which is embedded in a p-doped substrate, or a p-doped well which is embedded in an n-doped substrate. The well typically comprises four or five contacts which are arranged along a straight line and are disposed on the surface of the substrate. Two or three of the four contacts are current contacts which are used to allow a current to flow through the Hall sensor, and two of the other contacts are voltage contacts which are used to tap the Hall voltage which is produced in a magnetic field which extends perpendicular to the direction of the current and perpendicular to the surface of the semiconductor chip.
The most frequently used Hall sensors comprise four contacts or five contacts or, at most, six contacts and are sufficiently known from literature, including patent literature.
One of the most difficult tasks in the development of vertical Hall sensors was, and still is, determining the position and size of the contacts in such a way that the so-called offset of the sensor signal, which is the voltage present between the voltage contacts in the absence of a magnetic field, is as low as possible. This task will become the more difficult the thinner the well embedded in the substrate. This well, which represents the region of the Hall sensor which is sensitive to the magnetic field, is very thin with the current depth of a few micrometers and is becoming thinner and thinner with the progress in the miniaturization of the transistors. This problem therefore needs to be solved anew in each generation of IC technology.
In order to reduce the offset of a Hall sensor, two standard methods are known, which is firstly the orthogonal coupling of at least two Hall sensors, with the contacts of the first Hall sensor being “electrically displaced by 90°” in relation to the contacts of the second Hall sensor, and secondly the “Spinning Current Method”, in which the current and voltage contacts of the Hall sensor are exchanged in a cyclic manner. The orthogonal coupling is also known as parallel connection. These methods are known for example from the book “Hall Effect Devices, Magnetic Sensors and Characterization of Semiconductors” by Dr. R. S. Popovic, Adam Hilger, ISBN 0-7503-0096-5 and from EPFL Thesis No. 3134 (2004) by Enrico Schurig. The simultaneous application of both methods is known from WO 03/036733.